Electromagnetic Theory Questions and Answers – Relation of E,D,V

«
»

This set of Electromagnetic Theory Multiple Choice Questions & Answers (MCQs) focuses on “Relation of E,D,V”.

1. The electric flux density and electric field intensity have which of the following relation?
a) Linear
b) Nonlinear
c) Inversely linear
d) Inversely nonlinear
View Answer

Answer: a
Explanation: The electric flux density is directly proportional to electric field intensity. The proportionality constant is permittivity. D=ε E. It is clear that both are in linear relationship.
advertisement

2. The electric field intensity is the negative gradient of the electric potential. State True/False.
a) True
b) False
View Answer

Answer: a
Explanation: V = -∫E.dl is the integral form. On differentiating both sides, we get E = -Grad (V). Thus the electric field intensity is the negative gradient of the electric potential.

3. Find the electric potential for an electric field 3units at a distance of 2m.
a) 9
b) 4
c) 6
d) 3/2
View Answer

Answer: c
Explanation: The electric field intensity is the ratio of electric potential to the distance. E = V/d. To get V = E X d = 3 X 2 = 6units.
advertisement
advertisement

4. Find the potential at a point (4, 3, -6) for the function V = 2x2y + 5z.
a) 96
b) 66
c) 30
d) -66
View Answer

Answer: b
Explanation: The electric potential for the function V = 2x2y + 5z at the point (4, 3, -6) is given by V = 2(4)2(3) + 5(-6) = 96-30 = 66 units.

5. Find the electric flux density surrounding a material with field intensity of 2xyz placed in transformer oil ( εr = 2.2) at the point P(1,2,3) is
(in 10-10 units)
a) 2.1
b) 2.33
c) 2.5
d) 2.77
View Answer

Answer: c
Explanation: D = εE, where ε = εo εr. The flux density is given by,
D = 8.854 X 10-12 X 2.2 X 2(1)(2)(3) = 2.33 X 10-10 units.
advertisement

6. If potential V = 20/(x2 + y2). The electric field intensity for V is
40(x i + y j)/(x2 + y2)2. State True/False.
a) True
b) False
View Answer

Answer: a
Explanation: E = -Grad (V) = -Grad(20/(x2 + y2)) = -(-40x i /(x2 + y2)2 – 40(y j)/(x2 + y2)2) = 40(x i + y j)/(x2 + y2)2. Thus the statement is true.

7. Find the potential of the function V = 60cos θ/r at the point P(3, 60, 25).
a) 20
b) 10
c) 30
d) 60
View Answer

Answer: b
Explanation: Given V = 60cos θ/r. For r = 3m and θ = 60, we get V = 60cos 60/3 = 20cos 60 = 10 units.
advertisement

8. Find the work done moving a charge 2C having potential V = 24volts is
a) 96
b) 24
c) 36
d) 48
View Answer

Answer: d
Explanation: The work done is the product of charge and potential.
W = Q X V = 2 X 24 = 48 units.

9. If the potential is given by, V = 10sin θ cosφ/r, find the density at the point P(2, π/2, 0)
(in 10-12 units)
a) 13.25
b) 22.13
c) 26.31
d) 31.52
View Answer

Answer: b
Explanation: Since V is given find out E.E = -Grad(V) = – Grad(10sin θ cosφ/r). From E, we can easily compute D. D = εE = 8.854 X 10-12 X 5/2 = 22.13 units.
advertisement

10. If V = 2x2y + 20z – 4/(x2 + y2), find the density at A(6, -2.5, 3) in nC/m2.
a) 0.531i – 0.6373j – 0.177k
b) 0.6373i – 0.177j -0.531k
c) 0.177i – 0.6373j – 0.531k
d) 0.531i – 0.177j – 0.6373k
View Answer

Answer: a
Explanation: Find E from V, E = -Grad (V). We get E at A(6,-2.5,3) as 59.97i – 71.98j -20k. Thus D = εE = 8.854 X 10-12 X
(59.97i – 71.98j -20k) = (0.531i – 0.6373j – 0.177k) nC/m2.

Sanfoundry Global Education & Learning Series – Electromagnetic Theory.
To practice all areas of Electromagnetic Theory, here is complete set of 1000+ Multiple Choice Questions and Answers.

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

Subscribe to his free Masterclasses at Youtube & technical discussions at Telegram SanfoundryClasses.